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n 
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or  illustrated  impression. 


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conformity  avac  les  conditions  du  contrat  de 
filmage. 

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papier  est  imprimie  sont  filmis  en  commen9ant 
par  la  premier  plat  at  an  terminant  soit  par  la 
derniAre  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration.  soit  par  la  second 
plat,  salon  la  cas.  Tous  las  autres  exemplaires 
originaux  sont  filmAs  an  commandant  par  la 
premiere  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration  et  en  terminant  par 
la  darniire  page  qui  comporte  une  telle 
empreinte. 

Un  des  symboles  suivants  apparaitra  sur  la 
dernidre  image  de  cheque  microfiche,  selon  le 
cas:  le  symbols  — »•  signifie  "A  SUiVRE",  le 
symbols  V  signifie  "FIN  ". 

Les  cartes,  planches,  tableaux,  etc.,  peuvent  dtre 
film^s  A  des  taux  de  rMuction  diff Arents. 
Lorsque  le  document  est  trop  grand  pour  dtre 
reproduit  en  un  seul  clichA,  il  est  film*  A  partir 
da  Tangle  supAriaur  gauche,  de  gauche  A  droite, 
et  de  haut  en  has,  en  prenant  la  nombre 
d'images  nicessaira.  Les  diagrammes  suivants 
illustrent  (a  mAthode. 


1 

2 

3 

1 

2 

3 

4 

5 

6 

WvcbQiwQ  tor 
(3ol6  ^  ^  ^  ^ 


36?  a.  m.  IRoblnsoii 

Ob.  Bm.  Soc.  C.  £.,  /l^.  am.  Soc.  /Ift.  E. 


IRcprlntcD  fiom 

Cassier's  /lDaoaj»inc 

"Mew  JJorh 


^ 


CoUecUorv 


(Reprinted  from  Cassier's  Magazine.) 


DREDGING  FOR  GOLD 


By  A.  W.  Robinson,  M.  Am.  Soc.  C.  E.  and  M.  E. 


"PANNING  iiI'T" 

C()I.\C1I3KXT  with  the  dedine 
of  hydraulic  niininj^  for  gohl 
in  the  Oeat  West  of  the 
L'niterl  States,  is  the  rise  and  velop- 
ment  of  a  new  ])rocess  for  recoverinji; 
the  precious  metal  from  the  alluvial 
bottoms  and  river  beds  which  have 
heretofore  been  deemed  inaccessible. 
It  is  the  later  an<l  more  perfect  process 
succeeding::  the  earlier  and  cruder  one, 
and  it  makes  available  vast  deposits  of 
gold-bearinj;  j^^ravel  which  is  beyond 
the  reach  of  hydraulic  mining. 

1  lydraulic  mining  is  at  once  the  sim- 
l)lest  and  most  effective  method  of  sav- 
mg  the  bulk  of  the  gold  where  the  con- 
ditions exist  for  its  use :  but  more  or 
less  loss  occurs  in  the  tailings.  Hy- 
draulic mining  is  the  disintegration 
and  washing  down  of  a  bank  of  au- 
riferous gravel  by  mean-  of  a  jiowerful 
jet  of  water,  and  the  jiassing  of  the  re- 
sultant water  and  tichris  off  through  a 
sluice-box  containing  riffles  in  which 
the  gold  is  caught.  Two  essential  con- 
tliti<»ns  are  necessarv  to  successfullv 


operate  this  system  : — First,  the  water 
must  be  available  in  large  quantity  and 
under  heavy  pressure ;  and  secondly, 
there  must  be  a  "dump."  or  natural 
grade,  for  the  w  ater  to  run  ofif  and  de- 
posit the  tailings  without  interrui)tion. 

These  con<liti(jns  are  found  in  many 
places  along  the  banks  of  rivers  and 
creeks  and  in  the  valley  sides,  situated 
so  that  the  water  can  be  laid  on  by  a 
ditch  or  Hume,  which  taps  the  stream 
near  its  head  waters,  and,  following 
down  the  contour  of  the  valley  at  a 
gentle  grade,  is  soon  far  above  the 
river  bottom,  which  has  descended 
more  ra]Mdly.  A  pipe  line  car'-ies  the 
water  down  to  a  "giant"  nozzle,  which, 
bv  the  f(3rce  of  a  stream,  sometimes  as 
much  as  6  inches  in  diameter,  from  a 
pipe-line  i8  inches  in  diameter,  and 
with  a  pressure  of  several  hundred 
pounds  per  square  inch,  does  tremen- 
dous execution  in  washing  down  whole 
hillsides  and  spreading  them  out  in  the 
valley  below.  This  harnessing  of  the 
forces  of  nature  is  so  simple  and  eflfi- 
cacious,  so  free  from  complication,  and 
so  cheap  as  to  operating  expanses, 
that  handsome  returns  are  obtained, 
notwithstanding  its  wastefulness. 

This  simple  and  attractive  system 
soon  began  to  decline  for  the  reason 
that  the  localities  favored  by  nature 
became  grailuallv  exhausted  and 
worked  out.  Furthermore,  the  vast 
volumes  of  debris,  washed  down  into 
the  rivers  and  fruitful  valleys  below, 
became  a  menace  to  agriculture  and 
other  occupations,  so  much  so  that  the 
United  States  Government  ap])ointed 
the  "California  Debris  Commission" 
to  investigate  and  regulate  the  con- 
rticting  interests.  The  i)roceedings  of 
this  commission,  and  the  record  of  the 
strife  between  th<'  gold  miners  and 
the  land  and  navigation  interests,  fur- 
nish an  interesting  chapter  in  the  his- 
tory of  American  gold  mining,  par- 
ticularlv  in  California. 


4 


CASSIER'S  MAGAZINE 


DREDGING  FOR  GOLD 


5 


>» 


'I'hc  ^old  ill  those  placer  deposits  is 
in  the  form  of  tiiielv  (hvided  ])afticles, 
scattei-'.'d  throiij^h  the  j^'ravel.  The 
vahie  is  very  variable,  lo  to  15  cents 
per  cid)ic  yard  heint;'  accounted  ])oor 
^roitnd,  while  50  cents  to  $1  \V(nild  be 
rich  ])ay.  ( )ccasionally  pay  streaks 
are  found  which  will  run  $5  and  even 
$20,  or  more,  per  cubic  yard,  but  such 
streaks  do  not  represent  the  f^eneral 
averajn'e  of  a  deposit. 

A  cubic  yard  of  ,i;'ravel  and  sand  will 
weij^h.  about  2,800  ])oun(ls,  or  nearly  a 
ton  and  a  half,  h'ifty  cents'  worth  of 
i^o](\,  scattered  through  this  (piantity, 
at  $20  an  ounce,  will  wcijj^h  only  12 
.qrains.  The  proportion  of  ^^M  to 
jL;ravei  i)y  weit^ht  is,  therefore,  1  to 
1,630,000.  Inasmuch  as  sold  is  eleven 
times  as  heavy  as  t;favcl,  the  pro- 
portion bv  volume  would  be  1  to 
I  7,000,000. 

This  50  cents'  worth  of  ^old  is 
found  usually  in  finely  divided  par- 
ticles. If  the  particles  weijL^h  only  a 
j^rain  apiece,  it  is  called  "coarse"  fi-old 
and  can  lie  readily  saved  in  a  sluice- 
box,  altliout^h  the  ])articles  are  not 
larji^cr  than  ordinary  sand.  Fine  j^'old 
is  of  various  de.ti^rees  of  fineness  down 
to  minute  floating;  ])articles,  scarcely 
visible  to  the  naked  eye,  and  of  whicli 
it  re(piires  several  hundred  to  make  a 
cent's  value. 

The  marvelous  ease  with  which  the 
apparemly  infinitesimal  and  elusive 
yellow  jj^rains,  lost  amid  millions  of 
tons  of  earth  and  stones,  can  be  recov- 
ered is  due  to  the  t^^reat  specific  j.jrav- 
ity  of  ^o\(\.  ISeintj  eleven  times 
heavier  tlian  sand  and  nineteen  times 
heavier  than  water,  it  is  only  neces- 
sary to  wash  the  two  together,  when 
the  gold  sinks  to  the  bottom  and  the 
lijrhter  sand  and  tjravel  are  carried  ofif 
by  the  rushinji^  water. 

The  beautiful  simplicity  o{  the  hy- 
draulic sluicing  process  in  all  its  forms 
causes  it  to  be  the  most  widely  adopted 
of  any  method  of  jjold  saving.  Its 
efficiency  in  fine  gold  is  from  40  to 
60  per  cent.,  and  in  coarse  gold,  from 
70  to  100  per  cent.  If  the  gold  is 
wlioUy  coarse,  it  will  save  it  all. 

This  lack  of  cf^iciencv  has  led  manv 


invciUors  to  devise  means  to  :,ave  that 
fraction  of  the  tine  gold  that  is  lost  in 
sluicing,  but  thus  far  with  indifferent 
success.  Several  methods  of  amal- 
gamation have  been  successfully  used, 
but  for  thorough  work  their  capacity 
is  so  limited  that  they  do  not  pay. 

The  gradual  erosion  of  the  gold- 
bearing  banks  by  the  streams  and 
rivers  naturally  causes  a  deposition  of 
strata  lower  down,  containing  more  or 
less  gold.  These  alluvial  bottoms, 
sedimentarx  bars  and  beds  of  streams 
have,  until  recently,  been  considered 
as  beyond  the  reach  of  any  ordinary 
method  of  working. 

They  were  not  capable  oi  being 
washed  or  sluiced,  because  they  were 
alreadv  at  the  lowest  level.     X'arious 


THE   ROCKER 


attempts  to  dig  the  material  up  and 
elevate  it  into  sluices,  from  which  it 
could  be  worked,  were  made ;  but  the 
constant  presence  of  water  in  such 
workings  and  the  great  cost,  or  impos- 
sibility of  drainage,  rendered  such 
efforts  abortive.  Miners  were  com- 
])elled  to  be  content  with  scratching 
the  surface  or  sinking  shallow  pits 
until  overcome  by  the  water,  and 
speculating  upon  the  unknown  and 
untold  riches  that  lay  just  beneath 
their  feet. 

The  bottom  of  the  alluvial  deposit, 
or  "bed  rock,"  as  it  is  termed,  is  gen- 
erally where  the  richest  pay  is  found, 


• 


CASSIER'S  MAGAZINE 


(hit'  to  the  natural  ^gravitation  of  the 
gohl.  Thus  it  comes  about  tliat  atten- 
tion has  been  turned  to  dredtrintj  as  a 
method  of  reachinjj;'  these  deej)  and 
submerged  deposits  effectively.  ( )n 
the  face  of  it  a  simple  enough  problem. 


CLEANING  UP   A    SLUICE   BjX 

yet  what  vast  sums  have  been  sjient 
in  the  mistaken  efforts  of  those  who 
did  not  fully  appreciate  all  the  condi- 
tions involved,  and  how  elusive  the 
little  yellow  grains  are  when  attacked 
under  water !  The  seductiveness  of 
the  gold  attracts  many  to  engage  in  a 
mad  and  determined  search  f.  r  it.  and 
it  is  not  strange  that,  like  moths 
around  a  candle,  some  should  come 
to  grief. 

The  truth  is  that  gold  mining  is  a 
business  which  must  be  learned,  like 
any  other  business,  and  it  is  just  as 
amenable  to  the  natural  laws  which 
govern  it  as  any  other  of  the  practical 
sciences.  What  would  be  said  of  a 
tailor  who  engages  in  watch  making, 
or  of  a  merchant  who  endeavours  to 
design  a  bridge  or  a  locomotive?  Yet 
we  see  the  merchant,  the  manufac- 
turer, and  the  business  man  launch 


out  into  gold  mining,  and  make  sim- 
ple calculations  of  the  enormous 
wealth  that  can  be  taken  out  of  their 
claims  at  so  nnich  i)er  cubic  yard,  ;'tid 
assume  all  the  resi)onsil)ility  of  tiie 
practical  and  technical  work.  The 
primitive  mode  of  hand  wash- 
ing is  by  the  "pan," — a  shal- 
low dish  of  sheet  steel  about 
18  inches  across  and  3  inches 
dee]),  witli  a  tlat  bottom  and 
daring  sides.  Tlie  little  cut 
at  tlie  head  of  this  article 
shows  a  uiiner  panning  out 
some  samples  witli  which  lie 
seems  well  satisfied.  The 
nuich-uscd  ex])ression,  "pan 
out"  has  its  origin  in  the 
early  gold  -  mining  days, 
when,  after  careful  washing 
down  to  the  last  fine  par- 
ticles, the  results  in  the  pan 
were  eagerly  looked  for.  In- 
asmuch as  there  are  about  a 
hundred  ])ans  to  the  cubic 
yard,  it  will  be  seen  that  a 
cent's  worth  of  gold  to  the 
pan  would  be  valuable 
ground  when  worked  by 
modern  wholesale  methods. 

"Panning"  gold  is  a  sim- 
])le  and  rapid  oi)eration  to 
an  exj)enenced  miner,  but  to 
the  novice  it  is  slow  and  la- 
borious, liy  a  few  gyratory  move- 
ments with  the  li])  of  the  pan  under 
water  the  bulk  of  the  gravel  is 
(juickly  washed  over  the  i.^i\gi::  of  the 
pan,  while  the  gold  settles  to  the  bot- 
tom. The  jjrocess  is  then  continued, 
with  repeated  lap])ings  of  the  water 
carrying  off  a  little  sand  and  gravel 
each  time,  until  there  remains  only  a 
small  (|uantity  of  the  heavy  magnetic 
"black  sand"  always  found  in  gold- 
bearing  gravel.  In  this  sand  the  occa- 
sional gleam  of  a  "golden  colour"  is 
seen,  and  then  conies  the  interesting 
and  delicate  part  of  the  operation. 
Every  grain  of  black  sand  must  be 
carefully  washed  away,  leaving  the 
grains  of  gold  perfectly  clean. 

The  determination  of  values  can  be 
made  only  by  weighing  the  results  of 
a  large  number  of  pans,  .or  from  a 
definite  volume  of  material,  but  the 


f 


DREDGING  FOR  GOLD 


f 


iiutiihcr  of  "rolours"  to  a  pan  is  (jftcn 
usi'd  ti>  indicate  values.  A  "colour" 
is  a  particle  of  ^-old  apparent  to  the 
eye.  and  as  the  visible  ])articles  vary 
in  size  from  a  pin's  p(jint  upward,  they 
can  have  no  detinite  value. 

Xext  followinj,'-  the  "ijan"  is  the 
"rocker."  Tliis  is  the  ])ainiin_ij;-  o])era- 
tion  ])erfonned  continuously  in  a 
wooden  box  mounted  on  rockers,  and 
fitted  with  a  sieve  and  shelves  helow 
which  serve  as  sluice-boxes  for  catch- 
inj^-  the  ^old.  'i'he  miner,  as  shown  on 
I'''.i^^«-'  .^5.  J^hovels  the  t;ravel  into  the 
rocker,  then  rocks  it  with  one  Iiand. 
and  di])s  water  into  it  with  the  other. 
Many  wanderinj;-  miners  make  a  livinj^ 
by  "rockinj;"  out  the  surface  gravel 
in  selected  spots  along'  river  bars  and 
in  favourite  points  in  valley-bottoms. 


type  of  (lre(l).je  was  evolved  and  per- 
fected. 

.\hnost  every  known  type  of  dredge 
has  been  tried  for  gold  dredging.  One 
of  the  most  attractive  types  is  the  suc- 
tion, or  hydraulic  dredge,  which  sucks 
up  the  sand  and  gravel  with  a  large 
(piaiUity  of  water.  The  water,  thus 
pum])ed  up,  thereafter  serves  the  pur- 
])ose  of  sluicmg,  being  [vractically  one 
ojjeration.  There  is  ;i  difference  of 
opinion  concerning  the  utility  of  using 
a  ceiUrifugal  pumj),  or  suction  dredge, 
for  handling  gold-bearing  gravel.  It  is 
claimed  by  some  that  grains  of  gold 
can  be  elevated  and  carried  through 
the  discharge  i)ipe  of  the  pump,  be- 
cause the  velocity  of  flow  is  so  nuich 
greater  than  the  velocity  at  which 
grains  of  gold   will   fall   through   the 


PLAN    AND   SKCTION   OF    A   GOLD    UKEUGER 


I'Vom  these  primitive  methods  can.c 
the  suggestion  of  the  larger  and  more 
wholesale  methods  of  dredging.  It 
was  otily  necessary  to  combine  a 
<lredging  machine  and  a  sluicing  and 
washing'  a])paratus  in  order  to  reach 
at  once  these  precious  deposits.  The 
problem  proved,  however,  much  less 
simple  than  it  seemed,  and  many  ex- 
periments were  tried  before  the  final 


water.  This  is  true,  and  if  the  grains 
of  gold  could  be  introduced  mto  the 
mouth  of  the  suction  pipe  they  would 
assuredly  be  elevated  and  passed 
through  the  pump  into  the  riffles,  and 
would  there  be  caught. 

But  this  is  not  the  difficulty  with  this 
form  of  dredge.  The  difficulty  is  that 
the  force  of  the  suction,  being  intense 
close  to  tlie  suction  pipe  and  rapidly 


• 


CASSIER'S  MAGAZINE 


DREDGING  FOR  GOLD 


(k'criasitiLj  in  iiitt'iisity  a  short  distanco 
from  tlu'  siuiimi,  causi-s  all  tlu'  sand 
and  f^^avi'l  to  \k'  \nc\<vt\  up  and  Iravos 
till'  ^old  hrliind,  <hu'  to  its  j^rcatir 
spi'cilic  {gravity.  iMirthcnnorc,  lin' 
surtinn  drrdi,^'  cannot  work  in  stones 
or  howld'  rs.  The  nse  of  a  oentrifuffal 
])innp.  tlierefore.  for  cleanint:^  np  tlic 
hoitoin  and  piokini^  nji  the  ^old  is  ini- 
p.actieahle,  especially  if  the  f^old  he 
coarse  and  the  bed  rock  uneven.  A 
rotary  cutter  on  the  suction  pi|)e  does 
not  remedy  the  difticulty,  h.  .  ."^c  it 
oidy  ajj^itates  the  f^ravcl  and  in  her 
precipitates  the  j^old. 

'I'he  dii)per  dredj^e  has  nlso  heen 
used,  hut  in  most  cases  hrs  mccii  aban- 
doned, althout^h  it  is  an  admirahU  ma- 
chine as  a  dredj^e  and  will  handle  any 
ordinary  material.  It  is  noi  adapted 
for  placer-mining',  hecause  it  disturbs 
the  ).;ravel  in  the  act  of  di^.^Lnuj;,  so 
that  a  considerable  portion  of  the  jjold 
is  lost.  It  is  well  known  that  atjitation 
of  ,tj()ld-l)earint^  .gravel  imder  water  in- 
duces the  i)reci])itatinn  of  the  qcild  ;  in 
fact,  it  is  ])recisely  this  (pialily  on 
which  the  whole  operation  of  sluicini; 
and  j.j()ld  washinj^'  depends. 

it  is,  moreover,  mechanicailv  impos- 
sible to  construct  a  dip])er  dot^r  which 
will  be  absolutely  water-ti^ht.  Natur- 
ally, therefore.  luuch  of  the  tine  j^ravel 
in  the  bottom  of  the  (lii)per  leaks  out 
and  carries  .q'old  with  it.  X'arious 
packiuj.js  and  devices  for  makin.u:  tiie 
dip])er  door  water-tij.^ht  Inive  been 
tried,  but  none  are  successful.  A  cer- 
tain amount  of  hK)seness  is  necessary 
to  its  proper  workinjjf.  .V  bit  of  j.jravel 
would  prevent  a  tij^htly  fitted  door 
from  closinjjT,  and  it  would  inevitably 
become  loose  by  wear  in  any  case. 

.\nother  objection  to  the  dipper 
dredge  is  that  it  deposits  tlie  material 
intermittently,  several  tons  at  a  time, 
and  at  a  lontj  distance  from  the  centre 
of  the  dredi^e,  so  that  it  is  ditVicult  to 
take  care  of  the  material  delivered  in 
this  way.  It  is  necessary  to  have  a 
lar,i;e  hojjper  either  on  the  bank  or  on 
an  auxiliary  scow,  and  to  feed  the 
.i^ravel  out  of  this  hopper  into  sluice- 
l)oxes  or  other  a])l)lianccs. 

The  same  objections  a])]ilv  to  tlie 


clamslu'll  form  of  dredi,^'  to  an  even 
f^reater  de}.;ree,  as  it  is  by  no  means 
water-ti^ht,  and  loses  most  of  the  q;old 
in  the  act  of  brin^'inj.j  up  the  ^i^'ivel. 

In  the  elevator  dredge  none  of  the 
forej.;()in)4'  objections  are  found.  The 
action  of  the  endless  chain  of  buckets 
is  slow  and  (piiet.  and  the  material  is 
picked  up  clean  from  the  bottom  with 
the  smallest  amount  of  a};itation,  ami 
in  a  maimer  best  calculated  to  retain 
the  Ji'old.  The  buckets  are  water-tinht, 
and  retain  their  entire  contents  until 
emptied  by  inversion  at  the  top.  The 
delivery  of  material  is  continuous  and 
at  the  centre  of  the  boat,  instead  of  be- 
iiij;  intermittent  and  at  a  distance  over 
the  side  of  the  boat,  as  in  the  dii)per 
dredge.  The  elevator  buckets  also 
brin^  up  a  considerable  proportion  of 
water,  which  facilitates  the  washing? 
operation,  and  the  material  is  broujuht 
U])  in  smaller  masses  than  in  the  case 
of  the  dipper  (lredj.je,  and,  hence,  is 
..lore  easily  broken  and  disiutej^rated 
in  the  screen.  For  all  of  these  reasons 
it  is  the  ideal  type  of  drcd^t  for  river 
minin.LT.  This  conclusion  is  confirmed 
by  the  fact  that  all  the  c'redges  in  the 
Australian  and  New  Zealand  i^old 
fields  are  of  tiiis  type,  and  a  larj^e 
number  of  them  are  successfully  in 
use  there. 

The  elevator  or  chain  -  bucket 
dredq'e,  is  not  new  ;  in  fact,  it  is  one  of 
the  earliest  known  types.  Some  very 
good  dredf^es  of  ihis  type  were 
broujtjht  to  America  from  the  Clyde 
in  1832  for  use  on  the  river  St.  Law- 
rence. They  had  em^ines  of  the  side- 
lever  ty])c.  and  did  very  effective  work 
with  6  pounds  of  steam. 

On  the  opposite  pagfe  is  shown  a 
typical  jTold  drcdcfe.  This  machine 
consists  of  the  f(  illowint?  elements  : — 
1st.  the  dred^inq'  apparatus  proper. 
comprisin,q"  the  chain  of  buckets  and 
means  for  driviui^  them  ;  2(1,  a  steel 
ho]iper  into  which  the  material  is  dis- 
charjn;ed ;  3d,  a  revolving'  screen  in 
which  it  is  washed  and  by  means  of 
which  the  coarse  stones  arc  rejected ; 
4th.  a  sluice-box  for  carryin.q'  oi¥  the 
fine  tailings  and  dischargincf  them 
astern;    and    5th,  a  centrifugal  pump 


t 


# 


10 


CASSER'S  MAGAZINE 


i) 


AN    ELKCTHICALLY   OPERATED   URKDr.E 


for  furnishing'  the  necessary  water  for 
sluicing'  and  washing  purposes.  All 
these  details  have  been  successfully 
combined  so  as  to  make  a  complete 
machine,  capable  of  dredging  and 
treating  3,000  cul)ic  yards  of  material 
per  day.  The  operations  are  simple  and 
contiiuious,  and  tmder  perfect  control. 

The  vastness  of  the  field  thus  opened 
up  is  incalculable.  Thousands  of  miles 
of  good  gravel  deposits,  beyond  the 
reach  of  all  other  known  methods,  can 
now  be  made  available  at  a  low  work- 
ing cost.  One  of  these  dredges  can  do 
the  work  of  a  thousand  men  working 
in  the  old  way ;  and  not  only  that,  it 
can  reach  depths  and  clean  up  l)ed 
rock  that  would  be  totally  inaccessible 
by  the  cond)ined  labour  of  any  num- 
ber of  men.  The  work  of  gold  dredges 
has  already  become  a  perce[)tible  fac- 
tor in  the  world's  production  of  gold, 
and  it  is  yet  in  its  infancy  and  bound 
to  increase. 

Among  the  earliest  successful 
dredges  are  those  at  Bannock,  Mon- 
tana, on  Grasshopper  Creek,  in  the 
I'nited  States,  where  three  dredges  are 
at  work.  The  ground  is  not  phenom- 
enally rich,  varying  from  10  cents  to 


40  cents  per  cubic  yard ;  but  the 
dredges  have  maintained  a  steady 
average  of  work  which  has  yielded 
"clean-ups"  varying  from  $500  to 
S3000  ])er  day. 

On  ])age  34  is  shown  a  bird's-eye 
view  of  the  valley  of  the  Grasshopper 
with  one  of  the  dredges  in  the  dis- 
tance. The  creek  is  cjuite  small,  aver- 
aging 20  feet  wade  by  a  foot  deep ;  but 
the  dredges  work  out  the  whole  area 
of  the  valley  bottom  and  work  at  dif- 
ferent levels  controlled  by  dams. 

The  whole  field  of  dredging  for  gold 
is  yet  in  its  infancy,  and  it  offers  a 
promising  field  for  investment  under 
])ro])er  conditions.  A  large  amount  of 
))lacer-mining  ])roperty  yet  remains  to 
be  opened  up  that  can  be  worked  only 
by  dredging.  The  improvement  of 
modern  methods,  by  which  large 
capacity  can  be  maintained  at  low 
operating  cost,  renders  the  vvorking  of 
iow-grade  ground  possible  at  a  good 
profit.  The  proverbial  uncertainty  of 
mining  is  largely  eliminated,  and  by 
taking  ])roper  precaution  and  prv)ceefl- 
ing  on  business  principles,  dredging 
for  gold  becomes  sini|)ly  a  uianufac- 
turing  proposition. 


u^ 


DREDGING  FOR  GOLD 


tt 


f 


There  are  many  good  claims  and 
river  leases  lying  undeveloped  for 
want  of  capital  and  for  want  of  knowl- 
edge of  how  to  produce  certainty  of 
results.  ]f  the  results  can  be  assured 
with  reasonable  certainty,  capital  will 
not  be  slow  to  embrace  the  opportu- 
nity. Many  costly  experiments  have 
been  made,  some  of  which  have  been 
total  failures,  some  partial  failures  and 
some  successes.  Capitalists,  naturally 
and  wisely,  are  reluctant  to  put  money 
into  schemes  that  may  result  in  similar 
failure.  An  intelligent  examination  of 
these  cases  shows  that  in  every  in- 
stance failure  has  been  due  to  some 
evident  cause. 

Some  of  these  causes  are  the  fol- 
lowing : — 

1st,  the  ado])tion  of  the  wrong  type 


eral  arrangement  or  detail,  so  that  it 
fails  in  point  of  insufficient  capacity, 
frequent  breakdowns,  inability  to  dis- 
pose of  tailings,  inability  to  clean  "bed 
rock,"  inability  to  save  the  gold,  and 
excessive  cost  of  operation  in  propor- 
tion to  work  done;  4th,  poor  manage- 
ment ;  5th,  not  enough  gold  in  ground 
to  pay ;  6th,  organisation  by  a  "pro- 
moter" for  stock  jobbing  purposes ; 
7th,  operation  by  an  "inventor"  who 
has  a  new  machine,  and  can  do  what 
no  one  else  has  ever  done;  8th,  lack 
of  capital  to  efficiently  carry  on  the 
enterprise ;  9th,  ground  not  suitable 
for  dredging;  and,  10th,  character  of 
gold  such  that  it  cannot  be  commer- 
cially saved. 

"Forewarned  is  forearmed,"  and  to 
avoid  these  and  other  rocks  and  shoals 


^  ^ 


HVORAIXIC  SLLICING 


of  dredge,  such  as  suction,  clamshell, 
and  otlior  tuisiiitable  types,  which,  for 
specific  reasons,  cannot  be  made  a  suc- 
cess for  dredging  gold;  2d,  erroneous 
diagno'qs  of  the  conditions  to  be  ful- 
fiilc'  as  to  the  character  of  material 
and  method  of  working, and  the  conse- 
(|uent  lack  of  a(lai)tability  of  the  ma- 
chine to  those  conditions;  3d,  faulty 
design  of  the  machinery,  either  in  gen- 


it  1.-=  necessary  to  have  a  knowledge  of 
them.  It  is  i)ractically  impt)Ksil)le  for 
any  one  but  an  ex])ert  to  determine  all 
the  points  that  must  be  covered  from  a 
mechanical,  connnercia!  and  legal 
point  of  view  ;  but  enough  has  been 
said  to  indicate  the  general  character 
of  this  new  industry  and  ihe  lines  on 
which  it  can  be  successfully  carried 
on. 


